JP2012211913A - Reflection type photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type photoelectric sensor capable of determining a reflectance of an object to be detected, from the photoelectric sensor, in addition to detection of the presence of the object to be detected.SOLUTION: Light Pf emitted from light projection means to the object to be detected is divided into the first-sixth pulse lights Pf1-Pf6, as shown in Fig. 2(a), projection light amount E of the respective lights are made different each other, and the object to be detected is irradiated with the light Pf with a change rate ε1. The pulse light reflected by the object to be detected is received by photoreception means, to determine a change rate ε2 of received light amount W of the pulse light Pg shown in Fig. 2(b). The change rate ε2 of the received light amount W of the pulse light Pg is varied as shown in the Fig. 2(b) or Fig. 2(c), when the reflectance δ of the object to be detected is different, and therefore the reflectance δ of the object to be detected is selectively determined in response to the change rate ε2 of the received light amount W of the determined pulse light Pg, based on correlation data between the reflectance δ and the change rate ε2.

Description

  The present invention relates to a reflective photoelectric sensor that detects the presence or absence of an object by reflecting light emitted from a light emitting element by a detected object on the optical path and receiving the reflected light by a light receiving element. Specifically, the present invention relates to a reflective photoelectric sensor that can determine the reflectance of an object or the distance between the photoelectric sensor and the object.

  This type of reflective photoelectric sensor is frequently used to determine the presence or absence of an object, for example, in a production line of a factory. In a conventional reflective photoelectric sensor, light emitted from a light emitting element is irradiated through a light projecting lens onto a detected object such as paper disposed in front of the light projecting lens. The irradiated light is reflected by the surface of the object to be detected, and a part of the reflected light is received by the light receiving element through the light receiving lens, and this light is converted from an optical signal to an electric signal and further amplified by an amplifier. . Then, when the amount of the amplified light exceeds a preset threshold value, it is determined that there is an object to be detected.

  When light emitted from the light emitting element of the conventional reflective photoelectric sensor is constantly irradiated to the detection region, energy is wasted. Therefore, as shown in FIG. In FIG. 6 (b), the object to be detected is irradiated as a vertically-long rectangular pulse light having the same shape, and the reflected pulse light is attenuated and enters the light receiving element (see Patent Document 1). .

JP-A-6-132803.

  However, in the conventional reflective photoelectric sensor, the pulsed light emitted from the light emitting element has the same rectangular pulse waveform as shown in FIG. 6A, so that it is received by the light receiving element. Although the waveform of the pulsed light is attenuated as shown in FIG. 6B, it becomes a monotonous shaped pulsed light. For this reason, there has been a problem that only the presence / absence of the detected object can be detected based on the received pulsed light.

  The purpose of the present invention is to detect the amount of received light of each pulse light when a unit of light is irradiated to the detected object as a plurality of pulse lights, in addition to detecting the presence or absence of the detected object, and a predetermined predetermined level. , And the light projection amount of each pulsed light of the projected light when the light reception level changes from the predetermined level or less to the above can be determined, and the detected object from the photoelectric sensor based on this light projection amount It is an object of the present invention to provide a reflection type photoelectric sensor that can determine the distance to the distance.

  In order to solve the above problems, the invention described in claim 1 includes a light projecting unit that irradiates light to a detected object, a light receiving unit that receives light reflected from the detected object, and the light receiving unit. In a reflection type photoelectric sensor comprising presence / absence determination means for determining the presence / absence of the detected object based on the amount of received light, a plurality of pulse lights having different light emission amounts are sequentially emitted to the light projection means. Comparison between the received light amount control means for controlling the light operation, the received light amount comparison means for comparing the received light amount level of each pulsed light with a predetermined level for each light emitting operation, and the received light amount comparing means And a plurality of light receiving amount determining means for determining and outputting a light emitting amount of each of the projected pulsed light when the light receiving amount level changes from the predetermined level or less to the above, and a plurality of light receiving units present at different distances from the photoelectric sensor. Receipt by sensing object Distance storage means for storing the light emission quantity of the emitted pulsed light and the distances in association with each other when the quantity level changes from the predetermined level or less to the above, and the light emission quantity output from the light emission quantity determination means The gist of the present invention is to include distance determination means for determining the distance from the photoelectric sensor to the detected object by reading the distance corresponding to the information from the database stored in the distance storage means.

  The invention described in claim 2 is the light receiving amount storage means for storing the amount of light received by each pulsed light for each light projecting operation, and the amount of each pulsed light stored in the light receiving amount storage means. A rate-of-change discriminating unit that discriminates and outputs the rate of change of the received light amount from the amount of received light; a distance correcting unit that corrects the distance discriminated by the distance discriminating unit based on the rate of change discriminated by the rate-of-change discriminating unit; It is a summary to provide.

A gist of a third aspect of the present invention is that, in the first or second aspect, the light projection amount control means has a function of arbitrarily changing the number of pulse lights in each light projection operation.
A fourth aspect of the present invention is characterized in that, in the first or second aspect, the light projection amount control means has a function of arbitrarily changing the number of pulses in each light projection operation within a predetermined time. .

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the light projection amount control means is configured to arbitrarily set the light projection amount of each pulsed light in each light projection operation. Is the gist.

  According to the invention described in each claim, in addition to the detection of the presence or absence of the detected object, the received light amount level of each pulsed light when the light is irradiated to the detected object as a plurality of pulsed lights and a predetermined predetermined value By comparing with the level, it is possible to determine the light projection amount of each pulsed light of the projected light when the light reception level changes from the predetermined level or less to the above. The distance from the photoelectric sensor to the detected object can be determined based on the determined light projection amount. By determining this distance, for example, it is possible to determine the position, shape, or size of the detected object.

The block circuit diagram which shows 1st Embodiment of a reflection type photoelectric sensor. (A)-(c) is a graph explaining operation | movement of the photoelectric sensor of 1st Embodiment. The block circuit diagram which shows 2nd Embodiment of a reflection type photoelectric sensor. (A)-(c) is a graph explaining operation | movement of the photoelectric sensor of 2nd Embodiment. (A)-(c) is a graph explaining operation | movement of the photoelectric sensor of 2nd Embodiment. (A), (b) is a graph which shows the light projection waveform and light reception waveform of the conventional photoelectric sensor.

(First embodiment)
Hereinafter, a first embodiment of a reflective photoelectric sensor will be described with reference to FIGS.
The photoelectric sensor of the first embodiment is schematically shown in FIG. 1 in the detected object 11 conveyed by a conveyor of a production line that performs predetermined processing on the detected object 11 such as a workpiece. The light projecting means 12 for irradiating light, the light receiving means 13 for receiving the light incident on and reflected by the detected object 11, and the control device 14 for controlling the operations of the light projecting means 12 and the light receiving means 13 are configured. ing.

Therefore, each configuration of the light projecting means 12, the light receiving means 13, and the control device 14 will be described in order.
The light projecting means 12 includes a light emitting circuit 15, a light emitting element 16 connected to the light emitting circuit 15, and a light projecting lens 17. The light receiving means 13 includes a light receiving element 18, a light receiving lens 19 for guiding the light reflected by the detected object 11 to the light receiving element 18, and a light receiving circuit 20 connected to the light receiving element 18. ing. The light received by the light receiving element 18 is converted into an electric signal by the light receiving circuit 20 and amplified and sent to the control device 14.

  Next, the control device 14 will be described. The control device 14 includes a central processing unit (CPU) 21 that performs various types of arithmetic processing or discrimination processing. The CPU 21 is connected to a read only memory (ROM) 22 for storing various operation programs in advance, and is a readable / writable random access memory (RAM) as a storage means for storing various data. 23 is connected. The RAM 23 functions as a received light amount storage unit, a reflectance storage unit, and a distance storage unit. The CPU 21 is provided with a light projection amount control unit 24. The light projection amount control unit 24 uses the light projection amount control unit 24 to generate a first unit of light Pf that is projected by one light projection operation, as shown in FIG. The waveform is divided into sixth rectangular pulse lights Pf1 to Pf6, and the light emission amount E of each of the pulse lights Pf1 to Pf6 can be controlled so as to increase stepwise with the lapse of time t. The rate of change ε1 of the light projection amounts E1 to E6 of the pulse lights Pf1 to Pf6 can be set to a desired value. The rate of change ε1 is, for example, from the light projection amount E1 of the first pulsed light Pf1 per predetermined reference time tc, where the elapsed time from the first pulsed light Pf1 to the sixth pulsed light Pf6 is the reference time tc. This means the amount of change (E6-E1) in the light projection amount E6 of the sixth pulsed light Pf6.

  The CPU 21 is provided with presence / absence discriminating means 25 for discriminating the presence / absence of the detected object 11 based on the light receiving signal from the light receiving circuit 20. The presence / absence discriminating means 25 discriminates that the detected object 11 is present, for example, when the light receiving amount W6 of the sixth pulsed light Pg6 out of the first to sixth pulsed light Pg1 to Pg6 exceeds a predetermined value. Like to do.

  Further, the CPU 21 receives a unit of pulsed light Pg based on the received light amount W of the first to sixth pulsed lights Pg1 to Pg6 received by the light receiving means 13, as shown in FIG. A change rate discriminating means 26 for discriminating the change rate ε2 of the amount W is provided. The rate of change ε2 is the same as the rate of change ε1 described above, and the elapsed time from the first pulsed light Pg1 to the sixth pulsed light Pg6 is defined as the reference time tc, and the first pulsed light per the predetermined reference time tc. It means the amount of change (W6-W1) in the received light amount W6 of the sixth pulsed light Pg6 from the received light amount W1 of Pg1.

  Further, the CPU 21 has a reflectance determining means 27 for determining the reflectance δ of the detected object 11 based on the change rate ε2 of the received light amount of the pulsed light Pg determined by the change rate determining means 26. Is provided. This reflectance determination means 27 has the following functions. That is, even when the pulsed light Pf1 to Pf6 of the light Pf emitted from the light emitting element 16 is set to a constant change rate ε1 due to a difference in the color of the surface of the detected object 11 or a difference in surface treatment. For example, when the reflectance δ is high due to the difference in the reflectance δ of the detected object 11, the rate of change ε2 of the received pulsed light Pg increases as shown in FIG. 2B. On the contrary, when the reflectance δ of the detected object 11 is low, it is known that the rate of change ε2 of the received pulsed light Pg is small as shown in FIG. For this reason, the correlation data of the change rate ε1 of the projected light amount E of the projected light Pf, the reflectance δ of the detected object 11, and the change rate ε2 of the received light amount W of the received pulsed light Pg are previously tested. Or, use an appropriate theory. The correlation data is stored in advance in the RAM 23 as a database, and the reflectance δ corresponding to the determined change rate ε2 is selected from the database. The selected reflectance δ is displayed on the display device 28 connected to the control device 14. The display device 28 is configured to display the determination result of the presence or absence of the detected object 11 or other various data.

The CPU 21 is connected to an input device 29 for inputting various data such as the light projection amount control means 24, presence / absence determination means 25, change rate determination means 26, and reflectance determination means 27.
Next, the operation of the reflective photoelectric sensor configured as described above will be described.

  In FIG. 1, the light projecting means 12 is operated, the light emitting circuit 15 is operated by a control signal from the light projecting light quantity control means 24, and the change rate ε1 of the light projecting quantity E shown in FIG. Light Pf is emitted toward the detected object 11 at a predetermined cycle. The light Pf irradiated to the detected object 11 is reflected by the detected object 11 and received by the light receiving element 18. The received pulsed light Pg is input to the light receiving circuit 20 and converted from an optical signal to an electric signal. For example, as shown in FIG. 2B, the first to sixth pulsed lights Pg1 to Pg6 are present. Input to the discriminating means 25. The presence / absence discriminating means 25 discriminates whether or not the received light amount W6 of the sixth pulsed light Pg6 has reached a preset reference value, and if it has reached the reference value, the detected object 11 is present. As a result, it is displayed on the display device 28.

  On the other hand, the data shown in FIG. 2B transmitted from the light receiving circuit 20 to the CPU 21 is input to the change rate discriminating means 26, and the received light amount of the pulsed light Pg received by the change rate discriminating means 26. The rate of change ε2 of W is determined. The determined change rate ε2 is input to the reflectance determining unit 27, and the reflectance determining unit 27 uses the reflectance determining unit 27 to store the change rate ε1 of the light projection amount E stored in advance in the RAM 23, the reflectance δ of the detected object 11, and the like. Based on the correlation data of the change rate ε2 of the received light amount W of the received pulsed light Pg, the reflectance δ of the detected object 11 corresponding to the actual change rate ε2 is selected, and the selected detected object 11 is detected. The reflectance δ is displayed on the display device 28.

  By the way, when the reflectance δ of the detected object 11 is determined, when the detected object 11 is, for example, paper, differences in paper colors such as red, yellow, and blue can be determined. This can be used to determine the color difference of the detection object 11. Further, when the detected object 11 is, for example, various parts that have been machined, the reflectance δ varies depending on the finished state of the surface of the component. Therefore, by determining the reflectance δ, the surface finishing accuracy of the component can be improved. Good or bad can be determined.

According to the reflective photoelectric sensor of the above embodiment, the following effects can be obtained.
(1) In the above embodiment, the light intensity control means 24 is provided in the control device 14, and the light Pf of the first to sixth pulse lights Pf1 to Pf6 shown in FIG. 11 and the rate of change ε2 of the first to sixth pulsed light Pg1 to Pgn of the pulsed light Pg received by the light receiving unit 13 is determined by the rate of change determining unit 26. Further, based on the change rate ε2, the reflectivity discriminating means 27 causes the reflectivity δ of the detected object 11 to be changed to the change rate ε1 of the projected light amount E, the reflectivity δ of the detected object 11, and the received pulsed light Pg. Is selected from the correlation data of the rate of change ε2 of the received light amount W. Therefore, it is possible to easily determine the reflectance δ of the detected object 11 only by changing the function of the CPU 21 of the control device 14, and the reflectance δ can be used to determine, for example, whether the detected object 11 is good in color, processing accuracy, or the like. Can be determined.

  (2) In the above embodiment, the database representing the correlation among the change rate ε1 of the projected light Pf stored in advance in the RAM 23, the change rate ε2 of the received pulsed light Pg, and the reflectance δ of the detected object 11. The reflectance δ of the detected object 11 corresponding to the rate of change ε2 of the received pulsed light Pg is selected and set. Therefore, the reflectance δ of the detected object 11 can be properly determined, and a software program for controlling the operations of the change rate determining means 26 and the reflectance determining means 27 can be easily performed.

(Second Embodiment)
Next, a second embodiment of the reflective photoelectric sensor will be described with reference to FIGS. In addition, since 2nd Embodiment is the structure which changed the structure of the control apparatus 14 of the reflection type photoelectric sensor of 1st Embodiment, the detailed description is abbreviate | omitted about the same part.

  As shown in FIG. 3, the control device 14 includes the pulse light Pg <b> 1 to Pg <b> 6 generated by the light receiving unit 13 when the light Pf is irradiated from the light projecting unit 12 at a predetermined change rate ε <b> 1. A received light amount comparing means 31 is provided for comparing the levels of the received light amounts W1 to W6 with a predetermined level at which a predetermined detection object 11 can be detected. The received light amount comparing means 31 emits each of the pulsed lights Pf1 to Pf6 of the emitted light Pf when the level of the received light amount is changed from the predetermined level or less to the above by the comparison of the received light amount comparing means 31. A light projection amount discriminating means 32 for discriminating and outputting the light amounts E1 to E6 is provided. Further, the light quantity determining means 32 includes a distance determining means for determining the distance L from the photoelectric sensor (light projecting means 12) to the detected object 11 based on the light projection level determined by the light quantity determining means 32. 33 is connected. Further, the CPU 21 is provided with a distance correction means 34 for correcting the distance L based on signals from the change rate determination means 26 and the distance determination means 33.

Next, the functions of the received light amount comparing means 31, the projected light quantity determining means 32, the distance determining means 33, and the distance correcting means 34 will be described sequentially.
As shown in FIG. 4A, the change rate ε1 of the light projection amount E of the first to sixth pulse lights Pf1 to Pf6 of the light Pf irradiated from the light emitting element 16 to the detected object 11, and FIG. The distance from the photoelectric sensor to the detected object 11 even when the rate of change ε2 of the received light amount W of the first to sixth pulse lights Pg1 to Pg6 of the received pulse light Pg is the same as shown in FIG. Due to the difference in L, the waveform of the pulsed light Pg becomes different as shown in FIG. 4B or 4C. That is, when the distance L is short, the detected object 11 is also reflected normally, and the waveform of the received pulsed light Pg is the same as that of the projected light Pf as shown in FIG. The waveform is almost the same as the waveform. However, when the distance L is large, as shown in FIG. 4C, the first pulsed light that can be detected is detected by the attenuation of the light. For example, the fourth pulse light Pg4 corresponding to the fourth pulse light Pf4 is first among the pulse lights Pf1 to Pf6. Therefore, the first distance L1 when the first pulsed light Pf1 is first detected among the projected first to sixth pulsed lights Pf1 to Pf6 is defined as the first distance L1, and hereinafter the second to sixth The respective distances when the first and second pulse lights Pf2 to Pf6 are sequentially detected are set as the second to sixth distances L2 to L6, and these correlation data are obtained by experiments. Then, the correlation data is stored in advance in the RAM 23 as a database, and an arbitrary first detected from the correlation data by the received light amount comparison unit 31, the light projection amount determination unit 32, and the distance determination unit 33. One of the distances L1 to L6 corresponding to the pulsed light is selected.

  More specifically, in the second embodiment, the levels of the received light amounts W1 to W6 of the pulse lights Pg1 to Pg6 by the plurality of detected objects 11 existing at different distances L1 to L6 from the photoelectric sensor are the predetermined levels. The projected light amounts E1 to E6 of the projected pulse lights Pf1 to Pf6 and the distances L1 to L6 are stored in the RAM 23 as a database in association with each other. Then, the distance L4 corresponding to the light quantity (for example, E4 of the fourth pulsed light Pf4) output from the light quantity determining means 32 is read from the photoelectric sensor by reading out the distance L4 from the database stored in the RAM 23. A distance L4 to the detected object is determined. By determining the distance L4, for example, the height and width of the detected object 11 can be known.

  By the way, the above-described determination method of the distances L1 to L6 is applied when the rate of change ε2 of the received light amount W of the received pulsed light Pg is the same as the rate of change ε1 of the projected light amount E of the projected light Pf. However, as described above, when the reflectance δ of the detected object 11 changes, as shown in FIGS. 2B and 2C described in the first embodiment, the received light amount of the received pulsed light Pg. The change rate ε2 of W also varies. For this reason, in the second embodiment, the distance correction means 34 is provided with the following function so that an error does not occur in the determination operation of the distances L1 to L6 due to the difference in the change rate ε2 of the pulsed light Pg. ing.

  That is, as shown in FIG. 5A, when the rate of change of the received pulsed light Pg is the same rate of change as the reference rate of change ε2k, for example, as shown in FIG. 5B, the fourth pulsed light Pg4 Is detected first, as shown in FIG. 5A, when the change rate ε2 determined to be smaller than the change rate ε2k is small, the amount of received light W decreases. As shown in FIG. 5, the fifth pulsed light Pg5 is detected first. Therefore, when the determined change rate ε2 is different from the reference change rate ε2k, correlation data between the change rate difference between the change rate ε2 determined to be the reference change rate ε2k and the correction value of the distance L is obtained in advance through experiments or appropriate values. It is obtained by a simple theory, and this is set as a distance correction calculation formula, and this correction calculation formula is stored in the ROM 22. Then, the distance correction means 34 calculates the correction value of the distance L corresponding to the actual change rate difference based on the correction calculation formula.

In addition, you may change each said embodiment as follows.
In the first embodiment, a plurality of change rates ε2 of the received light amount W of the pulsed light Pg stored in the storage medium in advance and a plurality set according to each change rate ε2 with respect to the reflectance determination unit 27. The correlation data with the reflectance δ may be stored in advance as a database in a storage medium, and a function of selecting the reflectance δ according to the change rate ε2 determined from the database may be added.

  In the first embodiment, the reflectance determination unit 27 shown in FIG. 1 may be omitted. In this case, the change rate information of the received light amount output from the change rate determination unit 26 of the photoelectric sensor is transmitted to the reflectivity determination unit 27 provided in a control device different from the photoelectric sensor to determine the reflectivity. To do.

  In the second embodiment, the distance determination unit 33 and the distance correction unit 34 shown in FIG. 3 may be omitted. In this case, the light amount information output from the light amount determining unit 32 of the photoelectric sensor is transmitted to the distance determining unit 33 and the distance correcting unit 34 provided in a control device different from the photoelectric sensor, and the distance is determined. To do.

  In the second embodiment, when the determined change rate ε2 is different from the reference change rate ε2k, the correlation between the change rate difference between the determined change rate ε2k and the change rate ε2, and the correction value of the distance L Data is obtained in advance by experiment or appropriate theory, and this is stored in the RAM 23 as distance correction data, and the corresponding correction data is selected from the correction data by the distance correction means 34, and the actual change. A correction value for the distance L corresponding to the rate difference may be calculated by the distance determination means 33.

  In the first embodiment, the function of the light quantity control means 24 is set so that the light quantity of the first to sixth pulse lights Pf1 to Pf6 is gradually reduced from the light Pf shown in FIG. May be.

A function of arbitrarily changing the number of the plurality of pulse lights Pf1 to Pfn that form one unit of light Pf may be given to the light emission amount control means 24.
A function of variably setting the number of pulsed lights Pf <b> 1 to Pfn to an arbitrary number within a predetermined time may be given to the light emission amount control means 24.

  A function for variably setting each light projection amount of the pulsed light that forms one unit of light Pf to an arbitrary light projection amount may be added to the light projection amount control means 24.

  δ ... Reflectance, E, E1 to E6 ... Emission light quantity, L, L1 to L6 ... Distance, W, W1, W6 ... Received light amount, ε1, ε2, ε2k ... Change rate, Pf, Pg ... Pulse light, ε2k ... Reference Rate of change, Pf1 to Pf6 ... pulsed light, 11 ... object to be detected, 12 ... light projecting means, 13 ... light receiving means, 24 ... light quantity control means, 25 ... presence determining means, 26 ... change rate judging means, 27 ... reflection Rate discriminating means, 31... Received light amount comparing means, 32... Projected light quantity judging means, 33.

Claims (5)

A light projecting means for irradiating the detected object with light;
A light receiving means for receiving light reflected from the detected object;
A reflection type photoelectric sensor comprising presence / absence determination means for determining the presence / absence of the detected object based on the amount of light received by the light receiving means;
A light projection amount control unit that controls a light projection operation for sequentially emitting a plurality of pulse lights having different light projection amounts to the light projection unit, and
A received light amount comparing means for comparing the received light amount level of each pulsed light with a predetermined level for each light projecting operation;
A light projection amount discriminating means for discriminating and outputting a light projection amount of each pulsed light projected when the light reception amount level changes from the predetermined level or less to the above by comparison of the light reception amount comparison means;
A distance in which the projected light quantity of the projected pulsed light and the respective distances are stored in association with each other when the received light amount level of the plurality of detected objects existing at different distances from the photoelectric sensor changes from the predetermined level or less to the above. Storage means;
Distance determining means for determining the distance from the photoelectric sensor to the detected object by reading the distance corresponding to the light intensity information output from the light intensity determining means from the database stored in the distance storage means; A reflective photoelectric sensor comprising: The light receiving amount storage means for storing the amount of light received by each pulsed light for each light projecting operation according to claim 1,
A rate-of-change discriminating means for discriminating and outputting the rate of change of the received light amount from the received light amount of each pulsed light stored in the received light amount storage unit;
A reflection type photoelectric sensor comprising: a distance correction unit that corrects the distance determined by the distance determination unit based on the change rate determined by the change rate determination unit.   3. The reflection type photoelectric sensor according to claim 1, wherein the light projection amount control means has a function of arbitrarily changing the number of pulse lights in each light projection operation.   3. The reflective photoelectric sensor according to claim 1, wherein the light projection amount control means has a function of arbitrarily changing the number of pulses in each light projection operation within a predetermined time.   5. The reflection type photoelectric sensor according to claim 1, wherein the light projection amount control unit is configured to arbitrarily set a light projection amount of each pulsed light in each light projection operation. 6.